1. Field of the Invention
The present invention relates to a finder optical system for use in a silver salt processing camera, an electrically imaging camera and the like.
2. Description of the Related Art
In the field of the art for silver salt processing cameras and electrically imaging cameras and the like, there has been a wide use of the finder optical system which is structured independently from the image pickup lens system, in order to easily make the cameras compact and light-weight.
Since a camera of this kind, that is, so called compact camera (mostly being equipped with a lens shutter), has a separate finder objective lens for a finder optical system from an image pickup lens system, there arises a difference or shift between the two optical axes of the respective optical systems. This fact causes the disadvantage that two optical systems do not frame exactly the same view, making the view field of the finder different from the range to be taken and this will be of much significance and should be counted when the distance between a subject and the camera is short. This defective effect is called as parallax and has brought about difficulty in the art of the compact camera.
In order to eliminate this defect, there was proposed a camera apparatus which synthesizes the image signals from two image sensors disposed symmetrically with respect to the optical axis of the image pickup optical system, to thereby display an image free from parallax (Japanese Patent Application Laying Open (KOKAI) No. 63-121831). But since this camera apparatus employs image sensors, a complicated unit is needed for making and observing a colored taking image, thus increasing its cost. Moreover, observing the image to be taken, necessitates continuous use of electric power, resulting in a high consumption of battery.
For the reasons stated above, most cameras of this kind have dealt with taking a short-range picture by providing for the finder view field a parallax compensation mark at all times, or by providing a movable frame of view field for the finder optical system. However, these methods still exhibit a difficulty that the positional relationship between a subject to be taken and the background and foreground can not be obtained through the finder optical system.